Eloy noriega



E. NORIEGA.

. (No Model.)

MIGRGPHONB.

No.v 481,048. Patented Aug. 16, 1892.

/N VEN TOR 7 @yt/@m 1@ ATTORNEYS A UNITED STATES PATENT OFFICE.

ELOY NORIEGA, OF MEXICO, MEXICO.

MICROPHONE.

SPECIFICATION forming part of Letters Patent No. 481,048, dated August 16, 1892.

Application filed June 11, 1891.

T0 CZZZ whom/ it may concern:

Be it known that I, ELOY NORIEGA, of Mexico, Mexico, haveinvented a new and Improved Microphone, of which the following is a specification, reference being had to the annexed drawing, forming a part thereof.

The object of my invention is to construct a microphone which will faithfully transmit speech, whether low or loud, and will not re quire readjustment.

My invention consists in the composition for carbon microphones, hereinafter described and claimed.

The tubular handle A terminates in a dia phragm-cell a of ordinary form. The handle A is furnished with a tubular glass lining h, to which are loosely fitted carbon balls B. To the center of the diaphragm O contained by the diaphragm-cell a is attached a contactpiece d, which touches the first of the series ot` balls B. The last of the series of balls is supported bythe contact-piece e, resting on a springf, supported by a block g, contained by an insulating-cup h. The insulatingcup h is arranged to slide in the end of the tubular lining b and is adjusted by a screw c', inserted in the met-allie lining j, which incloses the end of the glass lining b. Abinding-post 7c at the end of the handle communicates with the block g and a binding-post Z oommunicates with the contact-piece d. The said binding-posts klare connected up in the local circuit of the telephone in the usual way-that is to say, with the battery and the primary wire of an induction-coil. Sounds projected against the diaphragm c alternately compress and release the series of balls B, so that the Serial No. 395,887. (No model.)

contact between the balls is varied and the resistance of the series is altered to correspond with the vibrations of the diaphragm.

The variation of the conductivity of the instrument produces electrical pulsations in the primary telephone-circuit, which induce currents in the secondary wire of the inductioncoil of the circuit, which, entering the receiving-telephone, represents the sounds uttered in the mouthpiece B.

The composition of the carbon used in my improved microphone is as follows: finelypowdered charcoal, ninety-nine parts; graphite, one part, and water, to which twenty per cent. of boric acid has been added, four parts. These ingredients are thoroughly mixed and pressed in molds of the desired form at a pressure of from seventy to one hundred atmospheres, finally baking the mixture according to methods well known in the manufactureot carbons. In some cases I may omit the graphite and use only charcoal with water and boric acid.

Having thus described my invention, I claim as new and desire to secure by Letters Patent- 1. A carbon for microphones, formed of charcoal, graphite, boric acid, and water in about the proportions stated.

2. A carbon for microphones, formed of charcoal, boric acid, and water in about the proportions stated.

ELOY NORIEGA.

Witnesses:

LUIS SANTA MARINA, J osE GARCIA. 

